Effects of Engineered Nanoparticles on Hydrophobic Organic Pollutants

E. Sahle-Demessie, C. Han, A. Zhao, H. Grecsek
U.S. Environmental Protectin Agency,
United States

Keywords: engineered nanoparticles, hydrophobic pollutants, adsorption, dispersion


As nanomaterials become increasingly part of everyday consumer products, it is imperative to measure their potential release during production, use, and disposal, and assess their impact on the health of human and the ecosystem. This compels the research to better understand how the properties of engineered nanomaterials (ENMs) lead to their accumulation and redistribution in the environment whether they could become emerging pollutants or can affect the mobility and bioavailability of other toxins. Organic pollutants, which are liquid at room temperature, associate with nanoparticles in an aqueous medium not only as molecules adsorbed on nanoparticles’ surfaces, but also as a discrete phase to form microscopic oil-nanoparticle aggregates. On the basis of our recent studies, pollutant-nanoparticle-aggregate formation is believed to be instrumental in an intended or unintended dispersion of organic pollutants. This knowledge would allow the use of environmentally friendly nanoparticles for cleanup of oil spills or other techniques such as surf washing. A better understanding of the nature and properties of pollutant-nanoparticle-aggregate will help predict the fate of pollutants in the aquatic environment. This work describes the various instruments and methods currently available for the detection and identification of pollutant-nanoparticle-aggregate. Moreover, the sorptive properties of ENMs were investigated with polyaromatic hydrocarbons. Organochlorine pesticides used as model pollutants. Linear Freundlich adsorption constants for the ENMs were correlated with the octanol-water partitioning organic pollutants. The suspended particles from water phase were separated, and the adsorbed substances were analyzed using a combination of thermal-chromatographic- mass spectroscopic techniques. Sorption of hydrophobic organic pollutants to nanoparticles increased the concentration of contaminants in the aqueous phase as compared to the "real" partitioning due to the octanol-water partitioning. The effects water chemistry on the partitioning of hydrophobic pollutants to ENMs was investigated. The effects of nanomaterials on the mobility of pollutants that are commonly found at many sites have been studied. These compounds include aromatic hydrocarbons, and two and three-ring polyaromatic hydrocarbons that have relatively small water solubility. The high partitioning coefficient indicated engineered nanomaterials have the potential to increase the mobility of hydrophobic pollutants in aquatic environment.